Tissue adhesive in the form of fibrin glues and sealants have been proposed for use to control bleeding, seal wound edges and to promote wound healing in a variety of traumatic and surgical situations. Furthermore fibrin sealants can be used to act as a biological matrix to facilitate and enhance cell survival, cell differentiation and cell proliferation, with emphasis on growth factors and stem cells. Fibrin glues or fibrin gels contain fibrinogen and thrombin which, when mixed together, form a solidified fibrin mesh of fibers, the basic substance of strength in hemostasis or clotting. Fibrin is used intra-operatively to affect hemostasis, sealing of wound edges or used as an adhesion prevention barrier.
In Europe and elsewhere commercial fibrin glues were prepared from fibrinogen and thrombin obtained from either pooling plasma cryoprecipitate from multiple human donors or from animal sources, e.g. Bovine. These products are prepared using laboratory drug regulated manufacturing processes including the need for pasteurization and filtration in order to eliminate harmful pathogens which might be transferred to the patient from such sources.
A further proven risk of these technologies is the risk of immune reaction originating from constituent parts associated to such pooled plasma sources. In addition the technologies are complicated by cold storage logistics, lengthy peri-operative processing times and cost especially at higher volumes. These reasons have caused such products to be used with extreme caution or withdrawn altogether.
In order to avoid the risk associated with pooled plasma sources, autologous fibrin glues, sealants or gels have been proposed where fibrinogen and thrombin are obtained from a single donor. Some of these fibrin products, however, had to rely on the combining of autologous fibrinogen with e.g. bovine thrombin, and thus still suffered from the risk or deficiencies associated with non-human products, e.g. an immune response against bovine plasma proteins.
For these reasons improved fibrin products and means for their preparation, where the fibrinogen and the thrombin components, were isolated from a single human donor blood or plasma sample for the use on that same donor have been proposed.
Several systems, tools or devices and methods as well have been brought forward and, at least for some of same, subsequently launched in order to satisfy this type of yet unmet medical need.
EP 0877 632 B1, for example, refers to a method for preparing stepwise autologous fibrin glue for surgical use and comprising centrifugation of the blood sample to afford a supernatant consisting mainly of plasma including fibrinogen, concentrating fibrinogen in the plasma fraction by means of centrifugation and subsequent filtration and eventually freezing the concentrated plasma before use. Fibrin glue is obtained by mixing the thawed concentrated plasma fraction with a “suitable starter”, indeed thrombin. Centrifugation is performed using interconnected plastic pouches constituting a closed system and the transfer of specific plasma fraction is indeed performed manually.
EP 1155 706 A1 discloses an apparatus for producing “clinically ready fibrinogen of high concentration” and discloses a closed system, in fact an apparatus provided with means for receiving blood concentration from a patient, a plasma membrane separator to extract and separate the plasma from undesirable components, a second membrane separator to provide separation of fibrinogen.
A vacuum pump is connected to the fibrinogen collector; a freezer is used to provide adjustable temperatures to the various plasma fractions; communication means comprise at least one peristaltic pump to maintain plasma transport within the closed system. According to a specific embodiment the system further comprises a mixer to mix fibrinogen with an adequate concentration of autologous thrombin and calcium salt to form the fibrin glue.
EP 1420 833 refers to a system (apparatus) for producing an autologous platelet gel which makes use of an autologous anti-coagulated blood sample as starting material and comprises, among others, a first vessel comprising means for activating the blood components which then provides coagulated blood components and expresses eventually thrombin therefrom.
The said first vessel is fitted with an external filter having a pore size that allows thrombin to pass through it selectively, the filtered thrombin being then mixed with a separate portion of autologous blood components like red blood cells, white blood cells, platelet rich plasma (PRP), platelet poor plasma (PPP) which all result from the centrifugation of the initial autologous blood sample and which are stored in a second vessel, to form autologous platelet gel.
All these solutions and their equivalents present some drawbacks: the simplest systems, e.g. as defined in EP 0877 632 B1, present the risks of disturbing the sterility inherent to hand manipulations, do not produce sufficient quantities to satisfy the needs of large surgeries, are impractical to operate during a surgical procedure, are too costly both in peri-operative labor input and materials and take too long thus not allowing the use of such systems during the course of the procedure.
Closed systems like those mentioned here above, or their equivalents, proved to be excessively complex to handle and to monitor, to be highly expensive in their use especially due to the necessity to clean and to decontaminate (if indeed possible at all) and to sterilize most of their parts for subsequent re-use and were therefore not adopted leaving ready to use recombinant or animal based products, stored frozen, as only practical, cost-economic technologies for surgeries requiring only small volumes of fibrin today thus still leaving an unmet medical need in those procedures, especially cardiac and orthopedic, requiring larger volumes >10 ml.
The invention obviates adequately all the obstacles still met in surgical process and responds to an obvious unmet medical need. The invention is defined in the claims appearing here below.